We propose a fast method for measuring optical properties, e.g., the refractive index profile and birefringence, of fibers. It is based on recovering the phase distribution of light refracted by a fiber sample at the recording plane from a single-shot digital hologram. During the recovering process, an optimized approach based on the spatial carrier frequency method was utilized. The proposed approach enhances affects that arise from the limited spatial extent of the bandpass filter associated with the implementation of the spatial carrier frequency method. In contrast to the low spatial resolution of off-axis digital holograms, the method ensures the best utilization of the camera support. From the recovered phase information, the optical path difference is measured; thus, the refractive index profile, the mean refractive index, and the birefringence of isotactic polypropylene (IPP) are determined. Experimental results are given for illustration.

Pluta polarizing interference microscope was used to follow the crazing that occur on the surface of stretched polypropylene fibres at different drawing conditions. The samples were stretched until crazing initiated, and then craze propagation was monitored as a function of drawing speed and test temperature. The effect of craze dimension on their propagation velocity was taken into account. Three-dimensional birefringence profile for crazed polypropylene fibre has been demonstrated to investigate the birefringence of crazed fibre at different test times for fixed drawing speed value. Also the mean birefringence values of crazed polypropylene fibres were calculated and the results showed that, these values increased with the areal craze density. Video images were used to calculate the craze velocity. Optical micrographs and microinterferograms were presented for demonstrations.

Influence of temperature on creep deformation for polypropylene PP fiber under a constant load was studied interferometrically. The automated multiple-beam Fizeau system in transmission was equipped with a mechanical creep device attached to a wedge interferometer. This system was used to determine the optical properties (n k , n ? , and Dn) of PP fiber during the creep process at constant loading with varying temperature. The creep compliance was drawn as a function of both time and temperature. An empirical formula was suggested to describe the creep compliance curves for PP fibers and the constants of this formula were determined. Two Kelvin elements combined in series were used to provide an accurate fit to the experimental compliance curves. The stress-strain curve via creep was studied to determine some mechanical parameter of PP fibers, Young's modulus E, yield stress r y , and yield strain e y . The optical orientation function f(y), the dielectric constant d, the dielectric susceptibility v, the surface reflectivity R, and the average work per chain W 0 were also calculated.

Multiple-beam Fizeau fringes in transmission were used to study the changes in optical parameters of thermally treated polypropylene PP suture fibers. Changes in the refractive indices and birefringence have been measured interferometrically on thermally treated PP suture fibers at temperatures of 19 to 40 AE 0.5 C. From the optical parameters; the mean polarizability of monomer units, the density, stress optical coefficient, the thermal stress and the activation energy of PP sutures were calculated. The results of density and optical measurements were used to calculate the crystallinity and the specific refractivity of the isotropic dielectric. Additionally, we calculated the mean square density fluctuation, the segment anisotropy, the molar refractivity and form birefringence. Relations between evaluated and measured parameters are given for illustration. The present study throws light on the changes due to slight thermal treatments as an example of thermal human end uses. Curves are given for illustration.

A two-beam interferometric method is used to study the change of optical orientation functions and the molecular structure of annealed Egyptian poly(ethylene terephthalate) (PET) fibers. The acoustic method was used for measuring the density. The density results were used to calculate the degree of crystallinity of PET. It was found that annealing causes alignment to the fiber chains in the directions of the fiber axis. This alignment gives an increase in the optical orientation function and decrease in orientation angle. The value of Da/3a 0 , which depends upon the molecular structure of the polymer, remains constant. The obtained results of the optical and the density clarify that new reorientations occurred due to annealing at different conditions. The changes of the refractive index profile of annealed PET fibers are given. Microinterferograms and curves are given for illustration.